1. Field of the Invention
The present invention relates to information processing of deterring information leakage.
2. Description of the Related Art
Recently, many corporations leak their customer's individual information, and such a violation of individual privacy has become a serious social problem. In that respect, interest in securities for the office information technology (IT) is growing.
To prevent confidential information from leaking outside a corporation, generally, access rights are set for digitized confidential information, or a monitoring device is added to a firewall. Alternatively, various measures are taken, and for example, personnel are inhibited from carrying, e.g., a notebook personal computer (PC) or a portable storage medium such as a USB (Universal Serial Bus) memory into or from an office.
Leakage of digitized confidential information can be prevented by deciding and executing monitoring policies as described above. For confidential information printed on a medium such as a printing paper sheet, however, it is more difficult to detect and inhibit carry-out of the printing paper sheet than for digitized confidential information. In other words, printed confidential information makes it difficult to maintain security.
To cope with this problem, various monitoring systems have been proposed. One of the monitoring systems stores image data printed on a printing paper sheet in a server at the time of printing by a printing apparatus, i.e., when the risk of information leakage via the printed matter has occurred. At this time, image data associated with attribute information such as the name of the user who has printed and the printing execution time is stored in the server. If information leakage via the printed matter has occurred, the server is searched for the image data corresponding to the leaked confidential information, thereby specifying the user who has printed the leaked confidential information on the printing paper sheet and the time of printing.
Another monitoring system adds attribute information such as user name and printing execution time to an image printed on a printing paper sheet using a digital watermark or two dimensional code at the time of printing. If information leakage via the printing paper sheet has occurred, and the image of the leaked information can be acquired, the user who has printed the leaked confidential information on the printing paper sheet and the time of printing can be specified using an apparatus for analyzing the digital watermark or two dimensional code.
The above-described monitoring systems have an effect of deterring information leakage and an effect of obtaining information useful for tracking of information leakage.
On the other hand, a user sometimes wants to avoid degradation in image quality caused by addition of a digital watermark or two dimensional code depending on the characteristic of an image to be printed. Japanese Patent Laid-Open No. 2005-072845 discloses a monitoring method of coping with a degradation in image quality by selectively using a visible barcode and an invisible digital watermark in accordance with the application purpose of a document. However, the method of Japanese Patent Laid-Open No. 2005-072845 still requires manipulation of an image itself. Hence, a demand has arisen for a method capable of preventing degradation in image quality in accordance with the characteristic of an image or document.
The degradation in image quality can be prevented by employing the monitoring system that stores image data printed on a printing paper sheet in a server at the time of printing by a printing apparatus. However, since all printed image data are stored in the server, the amount of image data stored in the server is enormous. It is therefore difficult to search for the image data of a printed matter that has caused information leakage.